refactor: Unify naming of direct/single/1:1/normal chats (#8442)

Unifies internal naming of single/direct/1:1/normal chats
to match the naming used in the API.

Closes: #8368
Signed-off-by: Jagoda Ślązak <jslazak@jslazak.com>

---------

Signed-off-by: Jagoda Ślązak <jslazak@jslazak.com>

deltachat-rpc-client/tests/test_securejoin.py

@@ -487,7 +487,7 @@ def test_qr_join_chat_with_pending_bobstate_issue4894(acfactory):
 def test_qr_new_group_unblocked(acfactory):
     """Regression test for a bug introduced in core v1.113.0.
     ac2 scans a verified group QR code created by ac1.
-    This results in creation of a blocked 1:1 chat with ac1 on ac2,
+    This results in creation of a blocked single chat with ac1 on ac2,
     but ac1 contact is not blocked on ac2.
     Then ac1 creates a group, adds ac2 there and promotes it by sending a message.
     ac2 should receive a message and create a contact request for the group.

deltachat-rpc-client/tests/test_something.py

@@ -275,7 +275,7 @@ def test_chat(acfactory) -> None:
     bob_chat_alice.unpin()
     bob_chat_alice.archive()
     bob_chat_alice.unarchive()
-    with pytest.raises(JsonRpcError):  # can't set name for 1:1 chats
+    with pytest.raises(JsonRpcError):  # can't set name for single chats
         bob_chat_alice.set_name("test")
     bob_chat_alice.set_ephemeral_timer(300)
     bob_chat_alice.get_encryption_info()